Electric fuel pumps disposed in a fuel tank of an automotive vehicle with a motor armature and commutator in contact with liquid fuel have been previously used. One such fuel pump with an electric motor having a flat commutator perpendicular to the axis of rotation of the armature and with brushes generally parallel to the armature is disclosed in U.S. Pat. No. 5,013,221 issued on May 7, 1991. Various flat commutator constructions and methods of making them have been previously used. U.S. Pat. No. 5,157,299 issued on Oct. 20, 1992 discloses a method and commutator in which circumferentially spaced apart separate carbon segments and underlying metal conductor/supports are received on a hub of a molded insulating plastic material with the plastic material received between the confronting side edges of adjacent metal conductor/supports to protect them from contact with liquid fuel which results in corrosion of the metal conductor/supports and degradation of the commutator when in service.
U.S. Pat. No. 5,386,167 to Strobl of Johnson Electric S.A. discloses a planar carbon segment commutator on a base member of an insulating material. The base member has a front surface extending, at least in part transversely to its rotational axis. Apertures extend rearwardly from the front surface and circumferentially spaced, independent contact members are individually mounted on the front surface. Each of the contact members has integral locking means which extend rearwardly into apertures in the front surface. Carbon segments are molded over the contact members so that each segment has integral anchor means, which extend rearwardly into the apertures in the front surface, by injecting a mixture of carbon powder and carrier material into the space between the base member and the mold. The patent states that any known carrier material, such as phenolic resin, may be used with the carbon powder to form the moldable mixture (column 2, lines 49-55).
The Strobl patent also says that subsequent heat treatment will depend on the operating requirements of different commutators, in accordance with known technology which forms no part of his invention. It is apparent, however, that subsequent heat treatments such as sintering will be restricted to temperatures far below those that would be optimal for the production of molded carbon articles such as carbon commutator segments in order to avoid degradation of the material in the insulating base member. Carbon powder mixtures such as those employed in this invention, and apparently in Strobl's, are typically sintered at temperatures of at least 1,000.degree. F., preferably at temperatures of about 1400.degree. F. to 1500.degree. F. Neither materials such as the phenolic resins conventionally used for commutator base members nor other known insulating materials that might be suitable for these structures will withstand these temperatures.